Glad to know that you upgrade the system to 1.4, from our experience there are quite a bit of changes requires to adapt to the new deployment model in 1.4 if I remember correctly.
The Deployment model "run detach" in AthenaX does not support reattach back to the job, we use REST API to do all the subsequent life-cycle management.
There are a couple of ways I can think of to workaround if upgrade to 1.5 is not an option:
- try to use CLI API  instead of REST API by replacing the life-cycle management component in WatchdogPolicy, so that you can trigger savepoints.
- try to modify the deployment model of AthenaX to not use "run detach" mode by modifying the "YarnClusterDescriptor"
Hope this can help your use case.